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Solar energy harvesting and storage are essential in the future mix of renewable energy technologies. Hierarchical coral-structured coatings have been shown to yield high solar absorptance in concentrating solar thermal (CST) systems. However, interfacial delamination and scalability challenges owing to material complexity pose significant hurdles for the widespread industrial adoption of these hierarchical CST coatings. Here, a coral-structured coating is proposed whose black pigments are strongly bonded by titania, which is a material that mitigates interfacial delamination. Importantly, this coating follows a facile deposition procedure suitable for large-scale solar receivers. The drone-deposited coating inhibits cation diffusion and maintains a stable solar absorptance of 97.39 ± 0.20 % $97.39\pm 0.20\%$ even after long-term (3000 h) high-temperature ( 800 ∘ C $800 \,^{\circ }\mathrm{C}$ ) aging. The scalability of developed coating represents a substantial advancement in the implementation of light-trapping enhancement and maintenance approaches across a wide range of CST applications.

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There is a general agreement among researchers that supercritical carbon dioxide (sCO2) cycles will be part of the next generation of thermal power plants, especially in concentrating solar power (CSP) plants. While certain studies focus on maximizing the efficiency of these cycles in the hope of achieving a reduction in electricity costs, it is important to note that this assumption does not always hold true. This work provides a comprehensive analysis of the differences between minimizing the cost and maximizing the efficiency for the most remarkable sCO2 cycles. The analysis considers the most important physical uncertainties surrounding CSP and sCO2 cycles, such as turbine inlet temperature, ambient temperature, pressure drop and turbomachinery efficiency. Moreover, the uncertainties related to cost are also analyzed, being divided into uncertainties of sCO2 component costs and uncertainties of heating costs. The CSP system with partial cooling (sometimes with reheating and sometimes without it) is the cheapest configuration in the analyzed cases. However, the differences in cost are generally below 5% (and sometimes neglectable), while the differences in efficiency are significantly larger and below 15%. Besides the much lower efficiency of systems with simple cycle, if the heating cost is low enough, their cost could be even lower than the cost of the system with partial cooling. Systems with recompression cycles could also achieve costs below systems with partial cooling if the design's ambient temperature and the pressure drop are low.

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In Concentrating Solar Power plants, reflective panels are used to redirect solar radiation towards a receiver. Because the panel shape drives the radiation distribution around the focus where the receiver is placed, the 3D measurement is fundamental to assess the panel shape quality. The VISproPT instrument is the advanced version of the prototype VISprofile; these instruments are designed for indoor measuring of the 3D shape of parabolic-trough reflective panels. The VISproPT hardware has been manufactured by MARPOSS Italia Spa and funded by EU project 'Solar Facilities for the European Research Area - Third Phase' (SFERA-III), while the image processing software as well as the calibration procedure, based on the measurement of a perfectly flat surface like that of a calm body of water, have been developed by the Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA). The instrument precision is better than 0.1 mrad and 0.3 mm (root mean square value over an area 1.2×0.8 m 2) for slope and height of the surface, respectively. Technical details of experimental set up and calibration-procedure are here reported. The instrument effectiveness is shown by reporting the results obtained on a set of 10 parabolic-trough specimens (5 inner + 5 outer) adopted to run the SFERA-III WP10 Task3 round-robin on 3D shape measurements among the different instruments used by the Fraunhofer Institute for Solar Energy Systems ISE (F-ISE), Deutsches Zentrum Fuer Luft - und Raumfahrt EV (DLR), the National Renewable Energy Laboratory (NREL) and Sandia National Laboratories (SANDIA).

The VISproPT is a novel instrument useful for scientists and technicians dealing with reflective panels for parabolic trough (PT) Concentrating Solar Power (CSP) plants. The VISproPT is an advanced laboratory instrument with high precision, designed to verify the shape compliance of PT panels. Deviations of slope and height from the ideal parabolic profile are evaluated and presented in terms of 2D contour maps as well as root mean square (RMS) values; these geometrical parameters are very useful to improve the production technology. Concerning the panel effectiveness in redirecting the solar radiation onto the linear receiver tube, the most representative parameter is the so-called intercept-factor (I-F), i.e. the geometrical intersection of the reflected solar beam with the receiver tube; the VISproPT software evaluates the I-F by considering the standard divergence of the solar radiation on the Earth (4.7 mrad half-apex angle) and the proper values of parabola focal-length and receiver-tube diameter; the I-F is reported as a 2D contour map and its mean value is calculated.

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Tantalum boride is an ultra-refractory and ultra-hard ceramic known so far for its favorable high-temperature thermo-mechanical properties and also characterized by a low spectral emittance, making it interesting for novel high-temperature solar absorbers for Concentrating Solar Power. In this work, we investigated two types of TaB2 sintered products with different porosities, and on each of them, we realized four femtosecond laser treatments differing in the accumulated laser fluence. The treated surfaces were then characterized by SEM-EDS, roughness analysis, and optical spectrometry. We show that, depending on laser processing parameters, the multi-scale surface textures produced by femtosecond laser machining can greatly increase the solar absorptance, while the spectral emittance increase is significantly lower. These combined effects result in increased photothermal efficiency of the absorber, with interesting perspectives for the application of these ceramics in Concentrating Solar Power and Concentrating Solar Thermal. To the best of our knowledge, this is the first demonstration of successful photothermal efficiency enhancement of ultra-hard ceramics using laser machining.

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Concentrating solar power (CSP) is considered as a promising renewable electricity source due to its superiority in providing dispatchable and base-load electricity. This study performs a systems process analysis to quantify the carbon emissions and nonrenewable energy costs induced by a state-of-art demonstration CSP plant located in the Tibetan plateau. Estimated to induce 111.2 g CO2 eq/kWh carbon emissions and 1.42 MJ/kWh non-renewable energy consumption, the CSP plant is considered to have extremely high carbon neutrality (88.8%) and energy renewability (86.4%). The prominent performance of carbon emissions reduction and energy conservation induced by the CSP plant shed light on its superiority of reliable power supply and environmental benefits. The plant is expected to cumulatively fulfill 3.4 million tons of carbon emissions reduction over its life cycle. In contrast to coal-based power and other renewable energy technologies, CSP technology is shown to be a promising solution to the low-carbon energy transition. Besides, a scenario analysis indicates that the incremental employment of CSP technologies will play a critical role in coping with climate change and energy security in China. Moreover, multiple policies to facilitate the development of the CSP system in China are elaborated, such as the promotion of integrated solar combined-cycle systems. The empirical finding draws a holistic picture of the carbon neutrality and energy sustainability performance of CSP technologies, and the systematic analysis in this study provides comprehensive policy perspectives for energy policy in the Tibetan region as well as in China in the context of global climate change.

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High-temperature concentrating solar power (CSP) system is capable of harvesting and storing solar energy as heat toward cost-effective dispatchable solar electricity. Solar selective coating is a critical component to boost its efficiency by maximizing solar absorptance and minimizing thermal emittance losses. However, maintaining a high solar-thermal conversion efficiency >90% for long-term operation at ≥750 °C remains a significant challenge. Herein, we report spray-coated spinel Cu-Mn-Cr oxide nanoparticle-pigmented solar selective coatings on Inconel tube sections maintaining ≥94% efficiency at 750 °C and ≥92.5% at 800 °C under 1000× solar concentration after 60 simulated day-night thermal cycles in air, each cycle comprising 12 h at 750 °C/800 °C and 12 h cooling to 25 °C. The solar spectral selectivity is intrinsic to the band-to-band and d-d transitions of nonstoichiometric spinel Cu-Mn-Cr oxide nanoparticles. This feature offers a large fabrication tolerance in nanoparticle volume fraction and coating thickness, facilitating low-cost and scalable spray-coated high-efficiency solar selective absorbers for high-temperature CSP systems.

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Algeria's energy demands are tremendously growing, and on the African continent it ranks among the countries with the highest energy consumption. To counter its growing energy demand, the country is progressively adopting renewable energy technologies, although conventional energy technologies still play a central role in its electricity production. The huge solar energy potential in Algeria can be exploited and utilized to meet the country's growing energy demand with minimal greenhouse gas production. Given that concentrating solar power is viewed as one of the most promising alternatives in the field of solar energy utilization, this study investigates the viability of a 100 MW parabolic trough-based power plant at Tamanrasset, Algeria. The plant was simulated in the System Advisor Model software considering the actual electricity load profile of the targeted location and implementing two different condenser types: evaporative and air-cooled. By comparing the plant's electricity production to the city's real load, the plant was in position of supplying about 78% and 60% of the city's electricity demand during the winter and summer seasons, respectively. The results show that implementation of such CSP plants could play an important role in meeting the energy demand as well as mitigating climate change through greenhouse emissions avoided in electricity generation process.

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In recent years, supercritical CO2 power cycles have received a large amount of interest due to their exceptional theoretical conversion efficiency above 50%, which is leading a revolution in power cycle research. Furthermore, this high efficiency can be achieved at a moderate temperature level, thus suiting concentrating solar power (CSP) applications, which are seen as a core business within supercritical technologies. In this context, numerous studies have been published, creating the need for a thorough analysis to identify research areas of interest and the main researchers in the field. In this work, a bibliometric analysis of supercritical CO2 for CSP applications was undertaken considering all indexed publications within the Web of Science between 1990 and 2020. The main researchers and areas of interest were identified through network mapping and text mining techniques, thus providing the reader with an unbiased overview of sCO2 research activities. The results of the review were compared with the most recent research projects and programs on sCO2 for CSP applications. It was found that popular research areas in this topic are related to optimization and thermodynamics analysis, which reflects the significance of power cycle configuration and working conditions. Growing interest in medium temperature applications and the design of sCO2 heat exchangers was also identified through density visualization maps and confirmed by a review of research projects.

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The scope of our study was to examine the potential of regeneration mechanisms of an aged molten Solar Salt (nitrite, oxide impurity) by utilization of reactive gas species (nitrous gases, oxygen). Initially, aging of Solar Salt (60 wt% NaNO3, 40 wt% KNO3) was mimicked by supplementing the decomposition products, sodium nitrite and sodium peroxide, to the nitrate salt mixture. The impact of different reactive purge gas compositions on the regeneration of Solar Salt was elaborated. Purging the molten salt with a synthetic air (p(O2) = 0.2 atm) gas stream containing NO (200 ppm), the oxide ion concentration was effectively reduced. Increasing the oxygen partial pressure (p(O2) = 0.8 atm, 200 ppm NO) resulted in even lower oxide ion equilibrium concentrations. To our knowledge, this investigation is the first to present evidence of the regeneration of an oxide rich molten Solar Salt, and reveals the huge impact of reactive gases on Solar Salt reaction chemistry.

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Enhancing the operating temperature of concentrating solar power systems is a promising way to obtain higher system efficiency and thus enhance their competitiveness. One major barrier is the unavailability of suitable solar absorber materials for operation at higher temperatures. In this work, we report on a new high-temperature absorber material by combining Ti2AlC MAX phase material and iron-cobalt-chromite spinel coating/paint. This durable material solution exhibits excellent performance, passing the thermal stability test in an open-air environment at a temperature of 1250 °C for 400 h and at 1300 °C for 200 h. The results show that the black spinel coating can offer a stable high solar absorptivity in the range of 0.877-0.894 throughout the 600 h test under high temperatures. These solar absorptivity values are even 1.6-3.3% higher than that for the sintered SiC ceramic that is a widely used solar absorber material. Divergence of solar absorptivity during these relatively long testing periods is less than 1.1%, indicating remarkable stability of the absorber material. Furthermore, considering the simple application process of the coating/painting utilizing a brush followed by curing at relatively low temperatures (room temperature, 95 and 260 °C in sequence), this absorber material shows the potential for large-scale, high-temperature solar thermal applications.

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This work deals with the application of femtosecond-laser-inscribed fiber Bragg gratings (FsFBGs) for monitoring the internal high-temperature surface distribution (HTSD) in solar receivers of concentrating solar power (CSP) plants. The fiber-optic sensor system is composed of 12 FsFBGs measuring points distributed on an area of 0.4 m2, which leads to obtain the temperature map at the receiver by means of two-dimensional interpolation. An analysis of the FsFBG performance in harsh environment was also conducted. It describes the influence of calibration functions in high-temperature measurements, determines a required 10 nm spectral interval for measuring temperatures in the range from 0 to 700 °C, and reveals wavelength peak tolerances in the FsFBG fabrication process. Results demonstrate the viability and reliability of this measuring technique, with temperature measurements up to 566 °C.

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Low-carbon power generation has been proposed as the key to address climate change. However, the sustainability and ecological efficiency of the generating plants have not been fully understood. This study applies emergy analysis and systems accounting to a pilot solar power tower plant in China for the first time to elaborate its sustainable and ecological performances. Emergy analysis covers virtually all aspects of sustainability and ecological efficiency by considering different forms of materials inputs, environmental support and human labor on the same unit of "solar joule". The input-output analysis based systems accounting is applied to trace the complete emergy embodied in the supply chain for all product materials of the given plant against the back ground of complex economic network, which improved the accuracy of accounting. This analysis illustrated unexpectedly low sustainability and ecological efficiency of this particular plant compared with the emergy analysis based on the primary materials (steel, iron, cement, etc.). Purchased emergy responses more than 95% of the total and emergy input in the construction phase is more than twice as much as that in the operation phase. Comparisons with other kinds of clean energy technologies indicate previous studies may have overestimated the sustainability and ecological benefits of low-carbon power plants. Thus, it is necessary to establish this kind of unified accounting framework. In addition, sensitivity analysis suggests that strictly controlling monetary costs of purchased inputs, extending service lifetime and improving power generation efficiency can promote higher sustainability and ecological efficiency for solar power tower plants. This study provides a more comprehensive framework for quantitative emergy-based evaluation of the sustainability and ecological efficiency for low-carbon power systems.

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Present environmental issues force the research to explore radically new concepts in sustainable and renewable energy production. In the present work, a functional fluid consisting of a stable colloidal suspension of maghemite magnetic nanoparticles in water was characterized from the points of view of thermoelectrical and optical properties, to evaluate its potential for direct electricity generation from thermoelectric effect enabled by the absorption of sunlight. These nanoparticles were found to be an excellent solar radiation absorber and simultaneously a thermoelectric power-output enhancer with only a very small volume fraction when the fluid was heated from the top. These findings demonstrate the investigated nanofluid's high promise as a heat transfer fluid for co-generating heat and power in brand new hybrid flat-plate solar thermal collectors where top-heating geometry is imposed.

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The redox cycle of doped CaMnO3-δ has emerged as an attractive way for cost-effective thermochemical energy storage (TCES) at high temperatures in concentrating solar power. The role of dopants is mainly to improve the thermal stability of CaMnO3-δ at high temperatures and the overall TCES density of the material. Herein, Co-doped CaMnO3-δ (CaCoxMn1-xO3-δ, x = 0-0.5) perovskites have been proposed as a promising candidate for TCES materials for the first time. The phase compositions, redox capacities, TCES densities, reaction rates, and redox chemistry of the samples have been explored via experimental analysis and theoretical calculations. The results demonstrate that CaCo0.05Mn0.95O3-δ showed an enhanced redox capacity (1000 °C at pO2 = 10-5 bar) without decomposition and provided the highest TCES density of ∼571 kJ kg-1 reported so far. The effective Co doping tended to increase the valence states of B-site cations in perovskite and facilitate the diffusion of the lattice oxygen atoms into the surface-active oxygen sites. Furthermore, the high cooling rates deteriorated the microstructure of CaCo0.05Mn0.95O3-δ particles and resulted in incomplete heat release, which is instructive to the design and operation of the TCES systems.

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The main objective of this paper is to present and analyze an innovative configuration of integrated solar combined cycle (ISCC). As novelties, the plant includes a recuperative gas turbine and the conventional bottoming Rankine cycle is replaced by a recently developed double recuperative double expansion (DRDE) cycle. The configuration results in a fuel saving in the combustion chamber at the expense of a decreased exhaust gas temperature, which is just adequate to feed the DRDE cycle that uses propane as the working fluid. The solar contribution comes from a solar field of parabolic trough collectors, with oil as the heat transfer fluid. The optimum integration point for the solar contribution is addressed. The performance of the proposed ISCC-R-DRDE design conditions and off-design operation was assessed (daily and yearly) at two different locations. All results were compared to those obtained under the same conditions by a conventional ISCC, as well as similar configurations without solar integration. The proposed configuration obtains a lower heat rate on a yearly basis in the studied locations and lower levelized cost of energy (LCOE) than that of the ISCC, which indicates that such a configuration could become a promising technology.

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Transition metal dichalcogenides (TMCs) exhibit unique properties that make them of interest for catalysis, sensing or energy storage applications. However, few studies have been performed into nanofluids based on TMCs for heat transfer applications. In this study, nanofluids based on 2D-WS2 are prepared by liquid phase exfoliation to analyze their potential usage in concentrating solar power plants. Periodic-Density Functional Theory (DFT) calculations were performed to rationalize the success of the exfoliation process. The hydrogen bond interaction between the hydroxyl group from PEG, which acts as a surfactant, and the S atoms of the WS2 surface stabilizes the nanosheets in the fluid. Electron localization function (ELF) analysis is indicative of the stability of the S-H interaction from WS2 with the molecules of surfactant due to the tendency to interact through weak intermolecular forces of van der Waals solids. Moreover, improvements in thermal properties were also found. Isobaric specific heat increased by up to 10% and thermal conductivity improved by up to 37.3%. The high stability of the nanofluids and the thermal improvements were associated with the high surface area of WS2 nanosheets. These results suggest that these nanofluids could be a promising heat transfer fluid in concentrating solar power plants.

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Nano-colloidal suspensions of nanomaterials in a fluid, nanofluids, are appealing because of their interesting properties related to heat transfer processes. While nanomaterials based on transition metal chalcogenides (TMCs) have been widely studied in catalysis, sensing, and energy storage applications, there are few studies of nanofluids based on TMCs for heat transfer applications. In this study, the preparation and analysis of nanofluids based on 2D-WS2 in a typical heat transfer fluid (HTF) used in concentrating solar power (CSP) plants are reported. Nanofluids prepared using an exfoliation process exhibited well-defined nanosheets and were highly stable. The nanofluids were characterized in terms of properties related to their application in CSP. The presence of WS2 nanosheets did not modify significantly the surface tension, the viscosity, or the isobaric specific heat, but the thermal conductivity was improved by up to 30%. The Ur factor, which characterizes the thermal efficiency of the fluid in the solar collector, shows an enhancement of up to 22% in the nanofluid, demonstrating great promise for CSP applications. The Reynolds number and friction factor of the fluid were not significantly modified by the addition of the nanomaterial to the HTF, which is also positive for practical applications in CSP plants. Ab initio molecular dynamics simulations of the nanoparticle/fluid interface showed an irreversible dissociative adsorption of diphenyl oxide molecules on the WS2 edge, with very low kinetic barrier. The resulting "decoration" of the WS2 edge dramatically affects the nature of the interface interactions and is therefore expected to affect significantly the rheological and transport properties of the nanofluids.

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Concentrating solar power (CSP) is a promising technology in Tunisia. However, its diffusion is facing many barriers which deter investments. Through the analysis of a CSP plant in Southern Tunisia by using the Global Risk Analysis (GRA) method, we try to analyze the main risks faced by investors. The main objective of this research is to identify and analyze the risks faced by CSP investors in Tunisia and develop strategies that should be adopted to accelerate the process of diffusion of this technology. This analysis allows us to conclude that the CSP project is very exposed to political, financial, physical-chemical, legal, and strategic hazards. Moreover, we show that among the four phases of the project, the preparation phase is the most vulnerable to hazards. In fact, the GRA method makes it possible to determine the list of the major risks, such as the risk of not obtaining permission to build a CSP plant, the risk of non compliance with the deadline, the risk of failure to achieve the expected performance, the risk of insufficient access to capital, and the risk of conflicts with local residents. In order to de-risk CSP technology in Tunisia, we propose some strategies, such as strengthening the public-private partnerships, using participatory approaches, creating local employment, etc.

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Nanofluids are systems with several interesting heat transfer applications, but it can be a challenge to obtain highly stable suspensions. One way to overcome this challenge is to create the appropriate conditions to disperse the nanomaterial in the fluid. However, when the heat transfer fluid used is a non-polar organic oil, there are complications due to the low polarity of this solvent. Therefore, this study introduces a method to synthesize TiO2 nanoparticles inside a non-polar fluid typically used in heat transfer applications. Nanoparticles produced were characterized for their structural and chemical properties using techniques such as X-ray Diffraction (XRD), Raman spectroscopy, Transmission Electron Microscopy (TEM), Fourier Transform Infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The nanofluid showed a high stability, which was analyzed by means of UV-vis spectroscopy and by measuring its particle size and ζ potential. So, this nanofluid will have many possible applications. In this work, the use as heat transfer fluid was tested. In this sense, nanofluid also presented enhanced isobaric specific heat and thermal conductivity values with regard to the base fluid, which led to the heat transfer coefficient increasing by 14.4%. Thus, the nanofluid prepared could be a promising alternative to typical HTFs thanks to its improved thermal properties and high stability resulting from the synthesis procedure.

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Research towards renewable energy sources is of great relevance in the pursue of environmental impact reduction and to decrease the dependency on fossil fuels. In high solar irradiation locations, the use of Concentrating Solar Power technologies might be a good alternative in front of other power sources. This study presents how multi-criteria methods such as the weighted technical analysis are useful to select the best heat transfer fluid to be used in a relatively small Concentration Solar Power plant in the Burkina Faso. To do so it analyzes three aspects, the technical performance of thermal fluids, their environmental impact and their price, giving them different weights to confer more or less relevance according to the idiosyncrasy of the region. To do the technical analysis, this study simulates the heat gain and temperature increase of four heat transfer fluids while passing through a solar parabolic trough. The environmental impact factor is evaluated following the life cycle assessment methodology and the economic factor compares their price in the market. Results show that Dowtherm A is the best choice for Burkina Faso and Marlotherm is the worst, but these results change considerably if the comparison is done in the USA, where the environmental factor gains relevance in contrast to the economic factor.

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